A large scale integrated circuit (LSI) is a component representing, or functioning as, an application processor of a smartphone.
Recently, in an LSI, as a driving voltage is lowered due to a decrease in power and an allowable power supply voltage for securing an operation of a system is decreased, the stability of a system with respect to power supply noise is reduced.
In addition, as a processing speed of LSI increases and functions are increased, an operating frequency increases and a sudden transient current may be generated in a power supply circuit. Thus, a frequency at which a voltage fluctuates increases and high frequency of a power supply noise increases, and a stability of a system may be reduced.
Therefore, in order to improve system stability of a high-performance LSI by reducing a change in a voltage and a power supply noise, it is advantageous to design power impedance to be low in a wide frequency band.
Power impedance is influenced by a design of a board and a decoupling capacitor. In detail, performance of the decoupling capacitor significantly affects power impedance.
In other words, in order to reduce power impedance, it has been necessary to lower equivalent series inductance (ESL) of the decoupling capacitor by as much as possible.